FIG 6.

Clofoctol inhibits the expression of pqs-controlled virulence traits. (A) Concentrations of HHQ (white bars) and PQS (gray bars) measured by LC-MS/MS on supernatants of PAO1 cultures grown for 16 h in LB in the absence or in the presence of clofoctol at the indicated concentrations. The averages from three independent experiments are reported, along with the SD. **, P = 0.0062; ***, P < 0.001 (ANOVA). (B to D) Effect of 100 μM clofoctol on pyocyanin production (B), swarming motility (C), and biofilm formation (D) in PAO1. The same phenotypes were evaluated in the ΔpqsR mutant as a control. For pyocyanin production in panel B, the averages from three independent experiments are reported with the SD, and representative supernatants are shown in the inset picture. ***, P < 0.001 (ANOVA). For the swarming motility (panel C) and biofilm formation (panel D), representative pictures of three independent experiments are shown. (E) Real-time RT-PCR analysis showing the mRNA levels of the indicated genes in PAO1 treated with 100 μM clofoctol (white bars) and in the ΔpqsR mutant (gray bars) relative to untreated PAO1. The averages from three independent experiments are reported with the SD. **, P = 0.0012; ***, P < 0.001 (ANOVA).